We are studying the genetic organization and expression of SV40 and adenovirus 2 by the analysis of the SV40 and Ad2 genomes contained within Ad2-SV40 hybrid virus DNA molecules. The hybrid viruses are also employed as models for understanding the behavior of integrated genomes. We are also analyzing the behavior of SV40 and Ad2-transformed and lytically infected cells as a function of the molecular conformation of viral nucleic acids within these cells, and as a function of events which may control viral replication, transcription, and translation. Secondly, we are analyzing the state and expression of the endogenous AKR murine leukemia virus genome in mice with varying expression of leukemia and virus production. A further objective is to explore the evolution, transmission, and relation to leukemogenesis of various murine RNA viruses. Finally, this laboratory is concerned with production and purification of Epstein-Barr virus DNA and the use of this reagent to explore molecular mechanisms of infection and oncogenicity associated with this human herpes virus.